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  • Organic Chemistry  (3,423)
  • AERODYNAMICS  (2,110)
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  • 1975-1979  (5,535)
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  • 1
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1, 4, 5, 6-Tetrahydro-ν-tetrazin-DerivateThe title compounds 2 and 13 are readily available from α-lithiated N-alkyl-nitrosoamines 1 (see Tables 1 and 2) which decompose at - 73° to yield the N-oxides 2. The ESR. spectra of two derivatives 1 are recorded (Fig. 1), and tentative mechanisms are proposed for the head to head dimerizations (la- 3- 4- 5- 2a and Scheme 1). Coupling of lithionitrosoamines with iodine (-6) and alternative decomposition routes of representatives of this class of organometallics with special substitution [equations (2)-(5)] are reported.The structures of the tetrazines are established by spectroscopic data [ESCA] (Fig. 2), IR., UV., 1H- (cf. Fig. 9) and 13C-NMR., PE. (Scheme 2), by an X-ray analysis of 2a (Fig. 4-8 and Table 3), and by the chemical reactions. The crystal structure of 2a is a twisted boat with non planar terminal nitrogen atoms which reflects the electron repulsion in the 4-atom-6-electron N—N=N≡N-system. Comparisons are made with 2-tetrazenes, the open chain analogues of 13, wherever possible. Raney-Ni reductions of 2 or 13 gives diamines 14 to which is assigned the d, l-configuration through the 1H-NMR. spectra of the aminals 7 and 15. Neither the oxides 2 nor the tetrazines 13 undergo cycloaddition reactions [equation (6) and Section 4].Compound 2a is dimerized to the bis (nitrosoamino)-2-tetrazene 18 by treatment with acid, ZnII, CuI or iodomethane. 2a is oxidized at nitrogen to the ethylene diamine derivative 6a (through 20, with H2O2), or at the CH2-groups of the ring to give oxo-N-oxide 21 (with MnO2 or the ring contracted oxo-tetrazoline-N-oxide 22 (with KMnO4).Pyrolysis or photolysis of the dimethyl tetrahydrotetrazine 13a furnishes the trimer 26 of N-methylimine, but no diazetidine 27. Silver and mercury complexes 29 are obtained from 13a, while Cr(CO)5. THF does not furnish a complex as with azocompounds, but rather replaces N2 in 13a by CO (→ 28). Oxidation with permanganate converts 13a into the oxalic acid derivative 30 with unchanged tetrazine structure.
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 61 (1978), S. 3050-3067 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1, 5, 6, 7-Tetrahydro-2H-[1, 4]diazepin-5, 7-diones from Malonimides and 3-Dimethylamino-2, 2-dimethyl-2H-azirineReaction of the aminoazirine 1 with malonimides of type 7 in 2-propanol at room temperature leads to the 1,4-diazepine derivatives of type 9 (Scheme 3). The structure of 6, 6-diethyl-3-dimethylamino-2,2-dimethyl-1,5,6, 7-tetrahydro-2H- [1,4] diazepin-5, 7-dione (9a) has been proved by single crystal X-ray analysis (Chapter 4). Reduction of the 7-membered heterocycle 9a with sodium borohydride yields the perhydro-[1,4]diazepin-5, 7-dione 10, while 9a in ethanol at 60° undergoes a ring contraction to the 4 H-imidazole derivative 11a (Scheme 4): Mechanisms of these two reactions are discussed in comparison with previously reported reactions (Chapter 5).
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 58 (1975), S. 1205-1207 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1,1-Dimethyl-2,3,4,5-tetraphenyl-1-silacyclohexa-2,4-diene is isomerized by iron pentacarbonyl to 1,1-dimethyl-2,3,4,5-tetraphenyl-1-silacyclohexa-2,5-diene. However, iron pentacarbonyl with 1,1-dimethyl-1-sila-cyclohexa-2,4-diene yields 1,1-dimethyl-1-silacyclohexa-2,4-diene-tricarbonyl-iron.
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  • 4
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Allyl sulfides and a selenide are metallated and silylated with chloro (penta-methyl)disilane. Treatment of the resulting disilanylmethyl sulfides 4 with trimethyloxonium tetrafluoroborate furnishes 1,1-disilyl-2-alkenes 5 in good yields. Some synthetic possibilities of 5 are outlined.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 317 (1975), S. 631-640 
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1,2,3-Triazabutadiene 3a-j existieren in zwei isolierbaren isomeren Formen, die aufgrund ihrer spektroskopischen und chemischen Eigenschaften als cis-trans-Isomere charakterisiert werden. Die Isomeren sind photochemisch ineinander umwandelbar, thermisch gelingt die Isomerisierung der cis- zur trans-Form nur bei den Verbindungen 3a-g. Die Quantenausbeuten von Hin- und Rückreaktion werden mitgeteilt.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 317 (1975), S. 712-720 
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Der massenspektroskopische Abbau der 1-Aryl-3-[3-methyl-benzthiazolinyliden-(2)]-triazene 1, die in zwei isomeren Formen existieren, wird untersucht. Die Isomerenpaare unterscheiden sich z. T. signifikant in der Intensität, mit der die Primärfragmentierungen ablaufen. Die Unterschiede werden im Hinblick auf eine mögliche cis-trans-Isomerie diskutiert.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 318 (1976), S. 671-680 
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: 1,2,3-Triazabutadienes. IV. MO Calculations of Photochromic TriazenesThe π-π* electronic transitions of different cis-trans isomers of substituted 1-aryl-3-(3-methyl-benzthiazolin-2-ylidene)-triazenes and of 1-(p-chlorophenyl)-3-(1,3-dimethylbenzimidazolin-2-ylidene)-triazene have been calculated by the PPP-method. The observed spectral characteristics can be described satisfactorily on the basis of a cis-trans isomerism around the N=N double bond. The Differences of the excitation energies between the cis and the trans form thus calculated render the experimental values with a deviation of ≤0.06 eV. The influence of the substituents on the energy of the S0 - S1 transitions has also been calculated and agrees in its tendency with the experimental results.
    Notes: Mit dem PPP-Verfahren werden die π-π*-Elektronenübergänge von verschiedenen cis-trans-Isomeren substituierter 1-Aryl-3-[3-methyl-benzthiazolinyliden-(2)]-triazene 1 und vom 1-(p-Chlorphenyl)-3-[1,3-dimethylbenzimidazoliyliden-(2)]-triazen 2 berechnet. Die beobachteten spektralen Eigenschaften dieser Verbindungen lassen sich befriedigend beschreiben, wenn eine cis-trans-Isomerie um die N=N-Doppelbindung zugrunde gelegt wird. Die so berechneten Anregungsdifferenzen zwischen cis- und trans-Form geben die expermentellen Werte mit einer Abweichung von ≤0,06 eV wieder. Der Substituenteneinfluß auf die Lage der S0 - S1-Übergänge wird ebenfalls in der Tendenz richtig dargestellt.
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  • 8
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1,2,3-Triazabutadienes. IX. 15N-NMR-spectroscopic Investigations of Cis-Trans-Isomeric 1-Aryl-3-[3-methylbenzthiazolinyliden-(2)]-triazenes and -triazenium-saltsThe 15N-chemical-shifts and coupling constants of systematically 15N-labeled cis-trans-isomeric 1,2,3-triazabutadienes 1a-c and triazenium-salts were determined and discussed with respect to the steric and electronic structure of the compounds. The chemical shifts correlate with the π-electron density calculated in PPP-approximation. The similarity of the chemical shifts and coupling constants of the respective alkylated and protonated compounds proves the preferred protonation of the trans triazabutadien chain in N1-position.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 319 (1977), S. 485-493 
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: 1,2,3-Triazabutadienes. V. Investigations of the Mechanism of the Thermal cis-trans Isomerisation of Substituted 1-aryl-3-[methylbenzthiazolinyliden-(2)]-triazenesThe velocity of the thermal cis-trans-isomerisation of substituted 1-aryl-3-[methyl-benzthiazolinyliden-(2)]-triazenes was determined, varying the substituents in the aryl resp. benzo residue, the temperature and the solvent.Electron- withdrawing substituents in ortho- resp. para-position of the aryl residue and electron-releasing substituents in position 6 of the benzo residue increase the velocity of isomerisation as it do polar solvents and acid catalyst. In the aryl residue electron-releasing substituted and in meta-position electron-withdrawing substituted derivatives do not thermically isomerise in solution under the given conditions.From these results a polar rotation mechanism of the isomerisation around the N=N-double bound of the triazabutadiene chain is concluded.
    Notes: Die Geschwindigkeit der thermischen cis-trans-Isomerisierung von substituierten 1-Aryl-3-[methylbenzthiazolinyliden-(2)]-triazenen wird in Abhängigkeit vom Substituenten im Aryl- bzw. Benzorest, von der Temperatur und dem Lösungsmittel bestimmt. Elektronen-akzeptorsubstituenten in o- bzw. p-Position des Arylrestes und Donatorsubstituenten in 6-Stellung des Benzorestes erhöhen die Isomerisierungsgeschwindigkeit, ebenso polare Lösungsmittel und saure Katalysatoren. Im Arylrest donator-substituierte bzw. in m-Stellung akzeptor-substituierte Derivate isomerisieren in Lösung unter den angewandten Bedingungen thermisch nicht. Aus den Untersuchungs-ergebnissen wird auf einen polaren Rotationsmechanismus der Isomerisierung um die N=N-Doppelbindung der Triazabutadienkette geschlossen.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 319 (1977), S. 813-826 
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: 1,2,3-Triazabutadiene. VI. Studies on the Cis-trans-Isomerisation of 1-Aryl-1-äthyl-3-(3-methylbenzthiazolin-2-ylidene) -triazeniumtetrafluoroboratesCis-trans-isomeric 1-aryl-3-[3-methylbenzthiazolinylidene-(2)]-triazenes will be alkylated under kinetic control stereospecifically to the corresponding cis-trans-isomeric 1-aryl-1-ethyltriazenium-tetraflouroborates 2. By their n.m.r.(1H and 13C)- and u.v.-vis.-spectroscopical as well as by their thermical and photochemical behavior the pairs of isomers are characterized as cis-trans-isomers about the N-1-N-2-bond. The rate of the thermal cis-trans-isomerisation depends from the substituents in 2 and from the solvent. Electron withdrawing substituents in para-position of the arylresidue and electron donors in the heterocycle increases the rate of the isomerisation. Morever it increases with an increasing DN-value of the solvent. The isomers can be changed into each other photochemically. The quantum yield of the cis-trans-isomerisation is evidently higher than of the trans-cis-transformation.
    Notes: Cis-trans-isomere 1-Aryl-3-[3-methylbenzthiazolinyliden-(2)]-triazene 1 werden unter kinetischer Kontrolle stereospezifisch zu den entsprechenden cis-trans-isomeren 1-Aryl-1-äthyl-triazeniumtetrafluoroboraten 2 alkyliert.Durch ihre NMR (1H und 13C)- und UV-S-spektroskopischen Eigenschaften sowie durch ihr thermisches und photochemisches Verhalten werden die Isomerenpaare als cis-trans-Isomere um die N-1-N-2-Bindung charakterisiert.Die Geschwindigkeit der thermischen cis-trans-Isomerisierung hängt von den Substituenten in 2 und vom Lösungsmittel ab. Para-ständige Elektronenakzeptorsubstituenten im Arylrest und Elektronendonatoren im Heterocyclus erhöhen die Isomerisierungsgeschwindigkeit. Sie steigt außerdem mit wachsender Donorzahl des Lösungsmittels an. Die Isomeren sind photochemisch ineinander umwandelbar. Die Quantenausbeute der cis-trans-Isomerisierung liegt deutlich über der der trans-cis-Umwandlung.
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